Entomologists Getting Antsy About Fire Ants' Trek Northward

June 03, 1992|by D'VERA COHN, The Washington Post

Fire ants -- tiny insects with a name that says it all -- are heading north, possibly as far north as Washington or Philadelphia.

Already, 335 of their mounds have been sighted in Virginia, including three in May. Eluding government inspectors, the ants have turned up on several shipments of southern-grown nursery plants sold in suburban Maryland.

Fire ants sting like a hot needle, and their bite can kill the 1 percent of people who are allergic to them. They can sting fawns, birds and other small creatures to death. Their mysterious attraction to electricity triggers blackouts or fires when they chew through insulation.

For years, it was thought that fire ants, which infest the South, could not live in the North because the winters here are too cold for them to survive. Now, however, some entomologists say that theory is crumbling. One reason is that the mounds where they live can stretch three feet underground, which is below the winter freeze line.

"I found out working with insects that you can project all you want, and the little devils will do what they want to," said John R. Tate, an entomologist for the Virginia Department of Agriculture. "If we have a (mild) winter like last winter, they can survive anywhere in Virginia."

"I'm now convinced they can survive as far north as Philadelphia," said Charles Staines, an entomologist in the Maryland Department of Agriculture.

Each mound can stand three feet high by five feet wide, with tunnels extending several yards out. A mound can harbor hundreds of thousands of ants, including thousands of queens, facilitating reproduction and making the insects harder to eradicate.

In Virginia, fire ants have been spotted at more than three dozen locations since 1989. Most appear to have hitchhiked aboard landscape plants from the South, Tate said. One shopping center had 150 mounds on its grounds.

In Maryland, the ants were found in three shipments of landscaping plants in 1989 and 1990.

The federal government has a quarantine against fire ants in the South, so plants and soil shipped across state borders are supposed to be inspected. The official policy in Maryland and Virginia is to eradicate the ants whenever they are found.

Fire ants are less than a quarter-inch long and look like ordinary ants. The variety spreading north is brownish-red, although there also is a black fire ant. Natives of South America, they are believed to have arrived in the United States on ships early in this century.

Aggressive ants, they swarm out stinging by the hundreds when their mound is disturbed, even by someone walking a few yards away. They do not die after stinging.